1. Field of the Invention
The invention relates to packaging films. More particularly, the invention pertains case ready packaging films having good antifog performance that are suitable for use in meat packaging.
2. Description of the Related Art
Containers have long been used to store perishable foods, such as meats, fruits and vegetables, prior to sale in the marketplace to consumers. Maximizing the time in which the food remains preserved in the containers minimizes the amount of spoilage.
The environment around which the food is preserved is an important factor in the preservation process. It is important that the food is maintained at an adequate temperature, while also controlling the molecular and chemical content of the gases surrounding the food. By providing an appropriate gas content to the environment surrounding the food, the food can be better preserved when maintained at the proper temperature or even when it is exposed to variations in temperature. This gives the food producer some assurance that the food will be in an acceptable condition when it reaches the consumer. Preferred modified atmosphere packaging systems for foods, including raw meats, exposes these foods to extremely low levels of oxygen because it is well known that the freshness of meat can be preserved longer under anaerobic conditions than under aerobic conditions. Maintaining low levels of oxygen minimizes the growth and multiplication of aerobic bacteria. Additionally, modified atmosphere packaging can involve high levels of oxygen, e.g. 80%, combined with nitrogen and/or carbon dioxide. The gases in these combinations do not favor bacterial growth but allow the raw meat to maintain a preferred red color that is acceptable to the consumer.
It is also important that the packaging exhibit good resistance to the formation of condensation inside the package on a surface of the film. This is known in the art as an antifog property. Multilayered films for modified atmosphere packaging having such antifog properties are well known and are commonly used when packaging food products having a high moisture content, such as fresh meats, and when it is important for the product to be clearly visible to the consumer. For example, U.S. Pat. No. 5,766,772 describes multi-layer heat-shrinkable films endowed with antifog properties having a different structure from this invention.
To produce a film exhibiting this antifog property, an antifog component is typically blended with or coated onto a sealant film such as a polyethylene film. This antifog-polyethylene component then forms a part of a multilayered packaging film, such as a nylon packaging film, that may also incorporate an oxygen barrier polymer layer such as ethylene vinyl alcohol. However, one significant problem associated with such known multilayered films having this antifog component is that the antifog component tends to be drawn toward polar materials, such as nylon, and away from the non-polar polyethylene. This is particularly a problem when the film is rolled up after manufacture such that the antifog layer or antifog containing polyethylene layer is brought into direct contact with an adjacent nylon layer. This causes the antifog component to migrate out of its existing polyethylene layer and into the nylon layer, compromising the performance of the nylon layer as well as degrading the antifog property of the film. Therefore, it would be desirable to have a multilayered packaging film having good antifog performance and having an antifog component which does not migrate into adjacent nylon layers when stored. The present invention provides such a solution to this need.